In the indoor and outdoor environments where people live and work, various kinds of electronic and electrical devices are deployed, such as multiple luminaires located at different locations. A user selects and controls these devices to satisfy his working and living requirements. Currently, people usually use immobile controllers, such as a control panel mounted on the wall to control these devices. In this case, if a user wants to control a device, he must go to the control panel to manipulate the button or knob corresponding to the device. As the number of devices increases, the control panel would become more complex with lots of buttons or knobs corresponding to the plurality of devices, and the user has to memorize which button controls the corresponding device. Although wireless communication technology has been used to shorten the distance between the user and the control panel, for example a remoter to control each device remotely, the remoter is still complex because of lots of buttons, menus or options for each device. So, the remoter is voluminous and its user interface is not very user-friendly.
In everyday working and living conditions, among a plurality of devices located in the same control area, a user usually just wants to select and control the device that is in a specific position with respect to him, such as at a specific distance from him or in a specific direction with respect to him. For example, when a user leaves the living room and enters the bedroom, he wants to turn on the luminaires in the bedroom, or turn off the luminaires in the living room; or he wants to turn on the luminaires at which his hand-held remoter is pointing, and maintain other luminaires unchanged. In the prior art, the wireless controller sends a probe message to detect all devices in its control area, and each device sends a respective feedback signal to the wireless controller according to protocols such as Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA). After the wireless controller has received feedback signals from all devices, it selects the target device located in the specific relative position by comparing the radio transmission information of the probe message or the feedback signals, such as Received Signal Strength Indicator (RSSI) or time of flight, and sends a control signal to the target device to control it. It is obvious that the existing system needs the feedback from all devices, and selects the target device in dependence upon all the various feedback received, even if the system just wants to select one target device in a specific distance or direction. As the number of devices increases, the amount of feedback signals also increases, thus the wireless controller needs more time to process and a higher processing capability; meanwhile, a large amount of feedback would increase the collision probability of the channel due to the random access method such as CSMA/CA, thus the wireless controller needs more time to collect all feedback signals from all devices. These drawbacks result in a longer delay before selecting and controlling the target device via the wireless controller, and in an unsatisfactory user experience.